US4691512A - Rotary hydrostatic machines or transmissions - Google Patents

Rotary hydrostatic machines or transmissions Download PDF

Info

Publication number
US4691512A
US4691512A US06/668,018 US66801884A US4691512A US 4691512 A US4691512 A US 4691512A US 66801884 A US66801884 A US 66801884A US 4691512 A US4691512 A US 4691512A
Authority
US
United States
Prior art keywords
casing
rotary
hydrostatic
pump
gear
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
US06/668,018
Inventor
Christian H. Thoma
George D. Mc. Arnold
Arthur A. Blair
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Unipat AG
Original Assignee
Unipat AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to GB838329441A priority Critical patent/GB8329441D0/en
Priority to GB8329441 priority
Priority to GB8332982 priority
Priority to GB838332982A priority patent/GB8332982D0/en
Application filed by Unipat AG filed Critical Unipat AG
Assigned to UNIPAT AG reassignment UNIPAT AG ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: ARNOLD, GEORGE D. M., BLAIR, ARTHUR A., THOMA, CHRISTIAN H.
Publication of US4691512A publication Critical patent/US4691512A/en
Application granted granted Critical
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Images

Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04BPOSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B23/00Pumping installations or systems
    • F04B23/04Combinations of two or more pumps
    • F04B23/08Combinations of two or more pumps the pumps being of different types
    • F04B23/10Combinations of two or more pumps the pumps being of different types at least one pump being of the reciprocating positive-displacement type
    • F04B23/103Combinations of two or more pumps the pumps being of different types at least one pump being of the reciprocating positive-displacement type being a radial piston pump
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01MLUBRICATING OF MACHINES OR ENGINES IN GENERAL; LUBRICATING INTERNAL COMBUSTION ENGINES; CRANKCASE VENTILATING
    • F01M1/00Pressure lubrication
    • F01M1/10Lubricating systems characterised by the provision therein of lubricant venting or purifying means, e.g. of filters
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16HGEARING
    • F16H39/00Rotary fluid gearing using pumps and motors of the volumetric type, i.e. passing a predetermined volume of fluid per revolution
    • F16H39/04Rotary fluid gearing using pumps and motors of the volumetric type, i.e. passing a predetermined volume of fluid per revolution with liquid motor and pump combined in one unit
    • F16H39/06Rotary fluid gearing using pumps and motors of the volumetric type, i.e. passing a predetermined volume of fluid per revolution with liquid motor and pump combined in one unit pump and motor being of the same type
    • F16H39/08Rotary fluid gearing using pumps and motors of the volumetric type, i.e. passing a predetermined volume of fluid per revolution with liquid motor and pump combined in one unit pump and motor being of the same type each with one main shaft and provided with pistons reciprocating in cylinders
    • F16H39/16Rotary fluid gearing using pumps and motors of the volumetric type, i.e. passing a predetermined volume of fluid per revolution with liquid motor and pump combined in one unit pump and motor being of the same type each with one main shaft and provided with pistons reciprocating in cylinders with cylinders arranged perpendicular to the main axis of the gearing
    • F16H39/18Rotary fluid gearing using pumps and motors of the volumetric type, i.e. passing a predetermined volume of fluid per revolution with liquid motor and pump combined in one unit pump and motor being of the same type each with one main shaft and provided with pistons reciprocating in cylinders with cylinders arranged perpendicular to the main axis of the gearing the connections of the pistons being at the outer ends of the cylinders

Abstract

A hydrostatic machine includes a casing (10) containing a rotary member (12) having radial cylinders (24) each with a piston (25) engaging a track ring (27). The member (20) is coupled to an external shaft (13) via reduction gearing (43,44) which also acts as a gear pump. This can be used to supply external power take-off fluid circuits, or an attached oil filter (64) or internal bearings (47,57) or make-up fluid for the machine via valve (42).

Description

This invention relates to rotary hydrostatic machines such as pumps and motors, or complete transmissions, and is particularly, though not exclusively, applicable to radial piston machines.
It is an object of the invention to provide an improved hydrostatic machine which may be particularly suitable for example to small-scale hydrostatic transmissions such as are used in horticultural tractors and will avoid some of the problems experienced with existing transmissions.
In many installations an auxiliary hydraulic oil circuit is necessary, and there may also be a need for reducing the rotational speed of the hydrostatic pump or motor or the transmission, and it is an object of the invention to alleviate some of the problems. A preferred embodiment satisfies both the requirements mentioned above in one and the same mechanism.
Broadly stated the invention consists in a hydrostatic machine including a casing containing a rotary member which provides generally radial cylinders each accommodating a piston which is actuated by a surrounding cam track as the member rotates and including transmission means for coupling the rotary member to an external shaft and means for supplying fluid to and from the cylinders as the member rotates.
The hydrostatic machine may be a pump or motor, and may conveniently be part of a hydrostatic transmission.
According to a preferred feature of the invention the machine includes reduction gearing acting between the external shaft and the rotary member, and preferably the reduction gearing also acts as a gear pump.
The gear pump may provide high pressure oil for external power take-off purposes, and alternatively or in addition it may provide oil for use as a boost pump for the machine within the casing. Conveniently the gearing is housed in a subsidiary casing attached to one end of the machine casing.
According to another preferred feature of the invention the casing has a mounting face onto which is secured a valve body for a directional control valve, and the valve may be sandwiched between the casing and an external filter or cooler. Preferably the connections between the machine itself, and the valve, and an external filter or cooler, are in the form of internal galleries or ports, without external pipework.
The output from the auxiliary pump may be arranged to supply a fluid system which may comprise some or all of the following elements:-
1. Directional flow control valve.
2. Auxiliary rams, actuators or motors.
3. Servo system(s).
4. Pressure relief valve(s).
5. Filter.
6. Cooler.
7. Main pump or transmission boost pump.
The invention may be performed in various ways and one specific embodiment will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a sectional plan view downwards of a hydrostatic transmission according to the invention,
FIG. 2 is a cross-section on the line A--A in FIG. 1,
FIG. 3 is a partial section on the line B--B in FIG. 1,
FIG. 4 is a partial section similar to FIG. 3 illustrating a modification,
FIG. 5 is a schematic sectional view of the spool valve,
FIG. 6 is a vertical sectional view through the spool valve on the line D--D in FIG. 2, and
FIG. 7 is a vertical sectional view through the spool valve on the line E--E in FIG. 2.
In this example the invention is applied to a rotary hydrostatic transmission for a small vehicle such as a garden or agricultural tractor. The transmission comprises a main case 10 containing a rotary hydrostatic pump 11 and a hydrostatic motor 12, the engine of the vehicle being coupled to drive an external input drive shaft 13 at one end of the casing with the output shaft 14 at the other end of the casing, coupled to the vehicle's driving wheels. The pump 11 and motor 12 are of generally similar construction. Each comprises a rotary cylinder block 20 attached to a ported sleeve 21 mounted to rotate on one end of a common fixed pintle 22, which is rigidly secured in a central sandwich plate 23 acting as an internal partition within the casing 10. Each cylinder block is formed with a number of radial bores 24 each containing a piston 25 attached to a slipper 26, which runs on a surrounding annular track ring 27. The two track rings are pivotally mounted on a common transverse pivot pin 28 and at least one of the track rings is connected by a movable hinge pin 30 to an actuating lever 31 attached to a control shaft 32 connected to an external manual transmission ratio control lever 33. Thus by turning the control lever 33 the eccentricity of the track ring 27 is altered in relation to the fixed pintle 22, thus altering the volumetric capacity of the pump and hence the transmission ratio of the complete machine.
The fixed pintle 22 has two internal longitudinal passages 37,38 each opening at opposite ends into an arcuate port 39,40 which communicates with respective cylinder bores 24 as the cylinder members 20 rotate. At one or both ends of the pintle there is provided a nonreturn valve 42 arranged to allow additional fluid to be drawn into the circuit for "make-up" purposes to replace any fluid lost by leakage.
The external input drive shaft 13 is keyed to a gear 43 located in an auxiliary casing 44, this gear meshing with a larger diameter gear 45 within the same auxiliary casing and keyed to the internal drive shaft 46, which is supported in hydrostatic bearings 47 and connected to a drive coupling element 48 provided with dogs 49 by which it is coupled to the rotary member 20. The two meshing gears 43,45 act as a gear pump and draw oil from a reservoir 50 up a feed passage 52 to a pump inlet 53. The high pressure oil delivered by the gear pump at outlet 54 passes to a supply passage 55 leading to a face 56 on the side of the casing 10. Some of this pressure oil is used to supply the hydrostatic bearings 47 and other bearings 57 on the shaft 13 and some of the oil also passes via a port 60 and a passage 61 in the end of the drive shaft 46, to provide oil for the non-return valve 42. A seal 62 is provided between the coupling element 48 and the sleeve 21 to maintain the oil pressure at the inlet valve 42.
Attached to the face 56 on the machine case is a directional control valve indicated generally at 63, the opposite side of the valve block being connected to an external oil filter or cooler unit 64, the three parts being rapidly held together by screw-thread anchorage studs 65. The internal functions of the valve are illustrated diagrammatically in FIG. 5 and the connections with an external power take-off circuit are illustrated in FIGS. 6 and 7.
As seen in FIG. 2, the pressure oil supplied by the internal gear pump through the delivery passage 55 passes into a central bore 70 in the valve body and thence through a non-return valve 71 to a passage 72 leading to the interior of the filter 64. The filtered oil returns from the filter 64 along the two passages 73, 74. Passage 73 leads to a pressure relief valve 76 which maintains the necessary operating pressure and returns excess oil back to the reservoir 50. The other return passage 74 supplies oil to the hydrostatic bearings mentioned above and also to the power take-off via the control elements of valve 63. The valve 63 includes a movable valve spool 77 which, as shown in FIG. 5, acts partly as a communication between the pump casing and the filter 64, and partly as a reversing valve between two output lines 78,79 leading to remote power take-off connections for an external pressure ram or the equivalent. These are illustrated in FIGS. 6 and 7.
The construction illustrated in FIG. 4 is basically similar to that in the illustrated example, but here the auxiliary gear pump pair 43,45 is replaced by a double stacked gear pair illustrated at 80,81. One pair of gears may be arranged to supply high pressure oil for power take-off purposes while the other pair runs at lower pressure for circulating oil through the filter cooler and provides boost pressure for make-up to the pump 11 via the non-return inlet valve 42. Preferably both gear pairs act in parallel and share the mechanical drive to the hydrostatic pump.
FIGS. 1 to 7 show a device designed to run as a "dry case" machine. This is preferred as a means of eliminating oil churning losses, which can be considerable at high rotational speeds.
However, the system may equally be applied to "wet case" machines offering a reduction in churning losses from the reduced input rotational speed.
In the illustrated example the gear pair acts as a reduction gear allowing reduced rotational speeds within the casing of the machine, but in some applications such as a low speed low power windmill transmission, the gear may be inverted to provide a step-up ratio. The auxiliary pumping action of the gear pair can however be maintained, the larger gear acting as the input driving element. In place of a conventional gear pair it is also possible to obtain the required results by a "crescent gear pump", having a small pinion engaging an internally toothed annulus gear.
In the illustrated example it will be seen that the valve body has aligned inlet and outlet ports on opposite faces and the external filter or cooler has similar aligned inlet and exit ports whereby the filter or cooler can be attached directly to the machine casing without the interposed valve body.

Claims (8)

We claim:
1. A hydrostatic machine including a casing, a rotary member for rotation within the casing and formed with generally radial cylinders each accommodating a piston connected to a slipper which engages a surrounding cam track as the member rotates, and including an external shaft, and transmission means including reduction gearing for coupling the rotary member to said external shaft, said reduction gearing comprising a relatively small diameter gear connected to said external shaft and a relatively large diameter gear connected to said rotary member, said reduction gear pair acting also as a fluid gear pump for supplying fluid under pressure.
2. A hydrostatic machine according to claim 1, in which said reduction gearing acts as a boost pump to supply pressure fluid to the cylinders of the rotary member within the casing.
3. A hydrostatic machine according to claim 1, wherein the larger diameter gear of said gear pair is secured to a transmission shaft which is coupled to said rotary member, and said transmission shaft is provided with an internal passage constituting the output flow passage from said gear pump.
4. A hydrostatic machine according to claim 3, in which said output flow passage communicates with a fluid inlet formed in a fixed pintle, on which said rotary member rotates, and including a fluid seal between said transmission shaft and said rotary member.
5. A hydrostatic machine according to claim 1, in which said reduction gearing provides high pressure oil for external power take-off purposes.
6. A hydrostatic machine according to claim 1, in which said gearing is housed in a subsidiary casing attached to one end of the machine casing.
7. A hydrostatic machine according to claim 1, which provides a hydrostatic transmission, said casing containing a hydrostatic pump and motor mounted concentrically on a common fixed pintle within the casing.
8. A hydrostatic machine according to claim 7, in which the said pump is connected to an external shaft through transmission means acting as reduction gearing and as a fluid gear pump and said motor is connected to an external drive shaft.
US06/668,018 1983-11-03 1984-11-05 Rotary hydrostatic machines or transmissions Expired - Fee Related US4691512A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
GB838329441A GB8329441D0 (en) 1983-11-03 1983-11-03 Hydrostatic transmissions
GB8329441 1983-11-03
GB8332982 1983-12-09
GB838332982A GB8332982D0 (en) 1983-12-09 1983-12-09 Hydrostatic transmissions

Publications (1)

Publication Number Publication Date
US4691512A true US4691512A (en) 1987-09-08

Family

ID=26286969

Family Applications (1)

Application Number Title Priority Date Filing Date
US06/668,018 Expired - Fee Related US4691512A (en) 1983-11-03 1984-11-05 Rotary hydrostatic machines or transmissions

Country Status (2)

Country Link
US (1) US4691512A (en)
DE (1) DE3440219A1 (en)

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0402585A1 (en) * 1989-06-12 1990-12-19 Tecumseh Products Company An internal reservoir-defining body for permitting oil expansion within a hydrostatic transmission housing
US4979583A (en) * 1987-07-04 1990-12-25 Thoma Christian H Variable speed transaxle
US4982566A (en) * 1990-02-22 1991-01-08 Von Kaler Roland Expander band for hydrostatic transmission
US5042252A (en) * 1990-02-22 1991-08-27 Unipat Ag Neutral shifting mechanism for hydrostatic transmission
US5078659A (en) * 1989-12-11 1992-01-07 Unipat Ag Variable speed transaxle
US5090949A (en) * 1989-12-11 1992-02-25 Unipat Ag Variable speed transaxle
US5182966A (en) * 1991-07-22 1993-02-02 Tecumseh Products Company Control mechanism for a hydrostatic transaxle
US5314387A (en) * 1991-07-09 1994-05-24 Hydro-Gear Limited Partnership Hydrostatic transmission
US5330394A (en) * 1991-07-09 1994-07-19 Hydro-Gear Limited Partnership Rider transaxle having improved hydrostatic transmission
US5505279A (en) * 1989-03-03 1996-04-09 Sauer Inc. Hydrostatic transmission and axle assembly
US5622052A (en) * 1993-10-19 1997-04-22 J.M. Voith Gmbh Double-flow hydrostatic radial piston engine with axial flow, thrust compensation, and shaft bearing
US6941753B1 (en) 1991-07-09 2005-09-13 Hydro-Gear Limited Partnership Hydrostatic transmission
US20050233852A1 (en) * 2002-05-31 2005-10-20 Hideaki Okada Hydrostatic transaxle apparatus
US20070225100A1 (en) * 2002-05-31 2007-09-27 Hideaki Okada Hydrostatic Transaxle Apparatus
US20080056887A1 (en) * 2006-06-09 2008-03-06 Entire Interest Hydraulic gear motor with integrated filter
US7537078B1 (en) 1989-03-03 2009-05-26 Sauer-Danfoss, Inc. Axle driving apparatus

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4843818A (en) * 1986-08-29 1989-07-04 Thoma Christian H Rotary hydrostatic machines or transmissions
DE4221705A1 (en) * 1992-07-02 1994-01-05 Voith Gmbh J M Hydrostatic machine with axial thrust compensation

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2220636A (en) * 1937-06-16 1940-11-05 Wilhelm Poppe Ag Hydraulic transmission gear
US2928295A (en) * 1955-04-22 1960-03-15 Boulanger Etienne Variable speed transmission device
US3165069A (en) * 1961-07-27 1965-01-12 Jaromir Tobias Hydraulic pressure automatic propulsion system
US3286464A (en) * 1964-06-04 1966-11-22 Dowty Technical Dev Ltd Hydraulic apparatus
US3299635A (en) * 1964-04-24 1967-01-24 Linde Ag Adjustable hydrostatic drive
US3411296A (en) * 1966-04-13 1968-11-19 Sundstrand Corp Hydrostatic transmission
US3645761A (en) * 1968-12-23 1972-02-29 Nippon Electric Glass Co Glass solder

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2220636A (en) * 1937-06-16 1940-11-05 Wilhelm Poppe Ag Hydraulic transmission gear
US2928295A (en) * 1955-04-22 1960-03-15 Boulanger Etienne Variable speed transmission device
US3165069A (en) * 1961-07-27 1965-01-12 Jaromir Tobias Hydraulic pressure automatic propulsion system
US3299635A (en) * 1964-04-24 1967-01-24 Linde Ag Adjustable hydrostatic drive
US3286464A (en) * 1964-06-04 1966-11-22 Dowty Technical Dev Ltd Hydraulic apparatus
US3411296A (en) * 1966-04-13 1968-11-19 Sundstrand Corp Hydrostatic transmission
US3645761A (en) * 1968-12-23 1972-02-29 Nippon Electric Glass Co Glass solder

Cited By (33)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4979583A (en) * 1987-07-04 1990-12-25 Thoma Christian H Variable speed transaxle
US5505279A (en) * 1989-03-03 1996-04-09 Sauer Inc. Hydrostatic transmission and axle assembly
US5979271A (en) * 1989-03-03 1999-11-09 Sauer Inc. Axle driving apparatus
US5921151A (en) * 1989-03-03 1999-07-13 Sauer Inc. Axle driving apparatus
US5802931A (en) * 1989-03-03 1998-09-08 Sauer Inc. Axle driving apparatus
US5542494A (en) * 1989-03-03 1996-08-06 Sauer Inc. Hydrostatic transmission and axle assembly
US7537078B1 (en) 1989-03-03 2009-05-26 Sauer-Danfoss, Inc. Axle driving apparatus
EP0402585A1 (en) * 1989-06-12 1990-12-19 Tecumseh Products Company An internal reservoir-defining body for permitting oil expansion within a hydrostatic transmission housing
US5078659A (en) * 1989-12-11 1992-01-07 Unipat Ag Variable speed transaxle
US5090949A (en) * 1989-12-11 1992-02-25 Unipat Ag Variable speed transaxle
US4982566A (en) * 1990-02-22 1991-01-08 Von Kaler Roland Expander band for hydrostatic transmission
US5042252A (en) * 1990-02-22 1991-08-27 Unipat Ag Neutral shifting mechanism for hydrostatic transmission
EP0443816A2 (en) * 1990-02-22 1991-08-28 Unipat Ag Expander band for hydrostatic transmission
EP0443816A3 (en) * 1990-02-22 1992-08-26 Unipat Ag Expander band for hydrostatic transmission
US20060026957A1 (en) * 1991-07-09 2006-02-09 Hydro-Gear Limited Partnership Hydrostatic transmission
US5423182A (en) * 1991-07-09 1995-06-13 Hydro-Gear Limited Partnership Improved hydrostatic transmission
US5330394A (en) * 1991-07-09 1994-07-19 Hydro-Gear Limited Partnership Rider transaxle having improved hydrostatic transmission
US5314387A (en) * 1991-07-09 1994-05-24 Hydro-Gear Limited Partnership Hydrostatic transmission
US6256988B1 (en) 1991-07-09 2001-07-10 Hydro-Gear Limited Partnership Rider transaxle having improved hydrostatic transmission
US6301884B1 (en) 1991-07-09 2001-10-16 Hydro-Gear Limited Partnership Brake design for a hydrostatic transaxle
US7065964B2 (en) 1991-07-09 2006-06-27 Hydro-Gear Limited Partnership Hydrostatic transmission
US6550243B2 (en) 1991-07-09 2003-04-22 Hydro-Gear Limited Partnership Hydrostatic transmission
US6672057B1 (en) 1991-07-09 2004-01-06 Hydro-Gear Limited Partnership Hydrostatic transmission
US6941753B1 (en) 1991-07-09 2005-09-13 Hydro-Gear Limited Partnership Hydrostatic transmission
US7036311B2 (en) 1991-07-09 2006-05-02 Hydro-Gear Limited Partnership Hydrostatic transmission
US20060026956A1 (en) * 1991-07-09 2006-02-09 Hydro-Gear Limited Partnership Hydrostatic transmission
US6526749B1 (en) 1991-07-09 2003-03-04 Hydro-Gear Limited Partnership Hydrostatic transmission
US5182966A (en) * 1991-07-22 1993-02-02 Tecumseh Products Company Control mechanism for a hydrostatic transaxle
US5622052A (en) * 1993-10-19 1997-04-22 J.M. Voith Gmbh Double-flow hydrostatic radial piston engine with axial flow, thrust compensation, and shaft bearing
US20050233852A1 (en) * 2002-05-31 2005-10-20 Hideaki Okada Hydrostatic transaxle apparatus
US7220204B2 (en) * 2002-05-31 2007-05-22 Hideaki Okada Hydrostatic transaxle apparatus
US20070225100A1 (en) * 2002-05-31 2007-09-27 Hideaki Okada Hydrostatic Transaxle Apparatus
US20080056887A1 (en) * 2006-06-09 2008-03-06 Entire Interest Hydraulic gear motor with integrated filter

Also Published As

Publication number Publication date
DE3440219A1 (en) 1985-05-15

Similar Documents

Publication Publication Date Title
US7722493B2 (en) Power-branched transmission and method for the operation of such a transmission
US2412588A (en) Gear divider with pressure loaded bushings
DE102004003335B4 (en) Engine oil system with variable pump
US5207060A (en) Tandem hydraulic motor
US4606428A (en) Transaxle differential
US6705840B1 (en) Inline tandem pump
US4471668A (en) Drive assembly with a prime mover and a flywheel
US7503173B2 (en) Control devices for swashplate type variable displacement piston pump
US2336911A (en) Power transmission and steering control for traction devices
US5555727A (en) Auxiliary pumps for axle driving apparatus including hydrostatic transmission
US3279172A (en) Hydraulic drive speed changing and transmitting unit
US5819535A (en) Charge pump and auxiliary pump for hydrostatic transmissions and integrated hydrostatic transaxles
US8272315B1 (en) Dual pump
US6682312B1 (en) Tandem pump and interface for same
US4686829A (en) Rotary hydrostatic radial piston machines
US3948049A (en) Dual motor hydrostatic drive system
US5421790A (en) Continuously variable transmission
US8393236B1 (en) Modular power distribution and drive system
US5492034A (en) Twin countershaft transmission and improved power take-off arrangement therefor
US3643433A (en) Hydraulic apparatus with interconnected hydraulic units
CA1040973A (en) Hydrostatic drive circuit
EP0183279A2 (en) Hydrostatic load-sense steering system
US3120814A (en) Variable delivery and variable pressure vane type pump
US20080202838A1 (en) Hydraulic Transaxle Apparatus For A Four-Wheel-Drive Vehicle and Four-Wheel-Drive Vehicle Using The Apparatus
US3785157A (en) Flow control dump valve

Legal Events

Date Code Title Description
AS Assignment

Owner name: UNIPAT AG, 4, BANKSTRASSE, CH-8750, GLARUS, SWITZE

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:THOMA, CHRISTIAN H.;ARNOLD, GEORGE D. M.;BLAIR, ARTHUR A.;REEL/FRAME:004364/0045

Effective date: 19841114

REMI Maintenance fee reminder mailed
LAPS Lapse for failure to pay maintenance fees
STCH Information on status: patent discontinuation

Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362

FP Expired due to failure to pay maintenance fee

Effective date: 19910908